WWDC2019 Session 615

Transcript

[ Music ]
>> Hello. I'm Ben Harry from the
Game Center Engineering team.
In this presentation, I'm going
to talk about Game Center player
identifiers.
To get started, I'm going to
give you a brief overview of
what Game Center offers to the
players of your games.
Game Center is a social gaming
network that allows players to
track their best scores on
leaderboards, view their
achievements earned playing your
games, challenge their friends
to complete an achievement or to
beat a leaderboard score, and
play either real-time or
turn-based multiplayer games
with their friends.
At the heart of Game Center
games are the players.
Players are represented by
objects that contain unique
information that differentiate
one player from another.
The object used to represent
Game Center players is the
GKPlayer.
Every GKPlayer has a unique
nickname accessed by the alias
property.
A player may also choose an
avatar image that will be used
within Game Center UIs.
In addition, each Game Center
user has a unique static
identifier that remains the same
across all games that the player
plays.
You may use this identifier to
store per-player information.
Let me now talk about how a
player static identifier
currently works in Game Center.
You may already be familiar with
this, but let us consider this
example in case you need to
refresh your memory.
Here we have two teams, Team A
and Team B.
In this presentation, I will be
using the term team to represent
a development team that releases
a game to the App Store using
App Store Connect.
So, I have been playing two
games from Team A and I also
really enjoy the game from Team
B.
As we see, my static Game Center
identifier is P123.
Each of these games we'll see
the same value from my
identifier P123.
No matter which game I play, I
had the same static identifier.
Going forward, we now want to
increase privacy by introducing
new player identifiers that are
scoped to the either the team or
the game itself.
So let's begin with the first of
these new identifiers, the team
player ID.
Remember that team refers to the
development team that releases a
game to the App Store.
Again, consider Team A and Team
B along with the same games from
before.
Notice that now I have two
different identifiers.
When I play either game from
Team A, the value of my team
player ID will be T11.
When I play the game from Team
B, the value of my team player
ID will be T22.
This means that the value of my
team player ID scoped to the
team that releases the game I
play.
This is an improvement to player
privacy as Team A will only know
my team player ID as T11, and
Team B will only know my team
player ID as T22.
So this is the team player ID.
I now want to tell you about our
other new player identifier, the
game player ID.
The game player ID is unique per
game per player.
This means that my game player
ID is unique to each game that I
play.
Its value is also independent
from the team that releases the
game.
Let us go back to our familiar
teams, Team A and Team B.
As you can see here, my game
player ID is different for each
game that I play, regardless of
which team has released the
game.
To further show how a game
player ID is independent from
the team, let's consider the
case when a game is transferred
from one team to another.
I am now going to show you what
happens to my scoped identifiers
when Game 2 is transferred from
Team A to Team B.
Let's say Team A transfers
ownership of Game 2 to Team B.
Now, when I play Game 2, my game
player ID for Game 2 remains
unchanged.
My game player ID for Game 2
persisted with the game and is
independent of the team.
Now, you may have also noticed
something about my team player
ID for Game 2.
My team player ID for Game 2
took on the value for Team B
since it is now released to the
App Store by Team B.
So we have come to the scoping
of the new Game Center
identifiers and also what
happens to these identifiers
when game ownership is
transferred.
I am now going to talk about how
you may use the scope
identifiers in the games that
you develop.
As you have seen, we have added
two new scope identifiers to the
GKPlayer, the team player ID and
the game player ID.
The team player ID and game
player ID have been introduced
with the goal of increasing
player privacy, which aligned to
the Apple's commitment to
protecting the privacy of our
users.
This new identifiers replaced
the existing static identifier
or player ID on a GKPlayer.
The playerID property is now
deprecated.
So I encourage you to start
using these new scope
identifiers today.
As I mentioned earlier, the team
player ID and game player ID
have been introduced to replace
the static player ID.
If you don't query the player ID
in your games, then you will not
need to make any changes.
If you do query the player ID,
you'll need to switch to the new
scoped identifiers.
You'll be using the team player
ID in most cases.
Likewise, if you currently use
the static player ID to save
game data, you should move to
the team scoped ID.
Doing so will handle the
situation in the device you
shared by multiple Game Center
players.
For those of you who may be
persisting the static player ID
in your own back end system, you
should also update to the new
scoped identifiers.
You can do this any time after a
successful authentication.
Next, let me show you how scoped
identifiers look for their local
player as compared to non-local
players.
As you probably know, the
GKLocalPlayer is the object that
represents the authenticated
Game Center player on a device.
At any given time, only one
player may be authenticated.
And the GKLocalPlayer has a
persistent team player ID and
game player ID.
But what about the GKPlayer?
A GKPlayer object provides
information about other players.
These are non-local players and
may be found in leaderboards
recently played lists
multiplayer matches and so
forth.
The scoped identifiers for
GKPlayers will be instance based
on the context in which they are
used.
For example, their scope to each
instance of a leaderboard or
each instance of a multiplayer
match, which means that you
cannot count on them to persist
in subsequent matches.
Let's say you have your own
player accounting system.
In which case, you'll be loading
the corresponding GKPlayer
objects.
To do this, use the
loadPlayersForIdentifiers:
withCompletionHandler method
found on GKPlayer.
You may use either the team
player ID or the game player ID
for the identifiers.
When you use the new
identifiers, there is a very
rare case where the scoped
identifiers will not be
available.
So what should you do if the
scoped identifiers are not
available?
Usually, when a player launches
one of your games, the scoped
identifiers for the local player
will be available after
successful authentication.
However, there is a slim chance
that the scoped identifiers may
not be available.
For this case, we've added a new
API to GKPlayer.
Scoped IDs are persistent.
This property will be false if
they are not available.
This means that you'll need to
check this property before using
the team player ID or game
player ID for the local player.
So let's tie all this
information together by
considering an example of using
the scoped identifiers after
successful authentication.
As you know, when the
authenticate handler returns,
you need to check if Game Center
has returned you a view
controller.
If so, then you present the view
controller when convenient.
If there is no view controller
and the local player has
successfully authenticated, then
you will be able to use the
scoped identifiers after first
checking the scoped IDs are a
persistent value.
If you are persisting the player
ID in your own back end system,
now is when you should convert
from the old static identifier
to the new scope identifiers.
I will now wrap up by
summarizing what I have
presented today.
Game Center is introducing new
scoped identifiers with the goal
of increasing player privacy.
A player's team player ID is
scoped to your development team.
A player's game player ID is
scoped to a game and will
persist with that game if it is
transferred from one developer
to another.
Use these new scoped identifiers
in Game Center APIs as you will
use the player ID.
Both of these identifiers are
available now so start using
them today.
For more information on this
presentation, please visit the
link shown here.
Thank you for watching.